GB2201232A - A valve - Google Patents

Abstract

A valve has within a chamber (11) a disc-shaped armature (8) mounted freely movably axially and with a centrally arranged sealing member (9). The armature (8) is moved axially by means of an electromagnetic field which can be induced by an exciting winding (19), whereupon the sealing member (9) is pressed against a sealing seat (3) at the end of a straight tubular portion (1) which is made of non-magnetic material. On its free end this tubular portion (1) has a connecting socket (2) for connection to a pipeline. The tubular portion (1) also passes through the exciting winding (19) so that the axes of the tubular portion (1) and the magnetic field lie parallel to one another. A preferably conical coil spring (12) acts against the armature (8) and tubular portion (1). At least one projection is provided inside the chamber (11), which extends towards the armature (8) and limits the travel of the axially movable armature (8). The valve housing, which bounds the chamber (11), only has one weld seam (17) and is attached to the casing (20) of the winding (19) by a cap which surrounds the valve housing and is screw-threaded at (22) onto the casing (20). <IMAGE>

Description

A Valve The invention relates to a valve with a housing and at least one valve seat provided therein and a sealing member which can be pressed against the valve seat, the sealing member being carried by a magnetisable armature and to displace the armature there is provided at least one exciting winding which can be connected to a power supply, the valve seat being provided at one end of a straight tubular portion which at its other end has means for connection to a pipeline, awd the sealing member is disposed in the centre zone of an armature whose plane of principal extension is at right angles to the axis of the tubular portion having the valve seat and the magnetic axis of the exciting winding lies parallel to the axis of this tubular portion and the armature is accommodated by the valve housing with clearance in peripheral direction, and a spring is provided between the tubular portion having the valve seat and the armature, one end of the spring being connected with the tubular portion and its other end with the armature, and the inner housing wall situated opposite the tubular portion having the valve seat has one or more projection near to the edge which protrude into the housing towards the armature and against which the armature is applied under the force exerted by the spring when the exciting winding is de-energised, and the valve housing is of multipart design and has a plane of separation, which lies on or parallel to the plane of principal extension of the armature.

Valves of this known type are referred to as solenoid valves, the magnetic force being applied by an energised exciting winding and serving both to lift the sealing member from the valve seat and to press it thereagainst. These valves have a valve housing with two diametrally arranged bores, with connecting means, for example with an internal thread, for connection to a pipeline. Further bores are provided transversely to these bores, wherein at least one of these transverse bores is disposed centrally in the housing and carries the actual valve seat which co-operates with the sealing member so as to effect a seal. The sealing member is itself secured at its end face to a shaft-like armature of ferromagnetic material, which projects into a cylindrical exciting winding and is mounted slidably therein.The magnetic forces induced by the excitation of the winding can displace the sealing body against the action of a spring. However, it is also possible to provide two exciting windings which can be actuated separately and to use exclusively electromagnetic forces both for opening and closing the valve. The shaft-like armature is here guided in the magnet coil over a considerable extent of its length and proper operation of the valve is dependent on the quality of this guide.

Specification DE-A-3424913: This prior publication discloses an electromagnetic valve for blood-pressure measuring instruments. A hollow cylindrical magnetic block accommodates a coil, the hollow cylindrical magnetic core of which has an air-inlet opening and an air-outlet opening. A star-shaped diaphragm of magnetic material is disposed in front of the air-outlet opening and it has a sealing washer on its side nearest the air-outlet opening.

This design may well be entirely adequate for the type of application referred to. However, a valve of this type is not suitable for use in vacuum installations, in particular in high-vacuum installations. This housing is not fluidtight, the entire electromagnetic coil is directly exposed to the medium, as is the supply cable. The wires of the winding and/or the varnished insulation thereof give off gases in the medium and nullifies the vacuum.

Specification DE-A-3227613: This prior publication illustrates and discloses a solenoid valve with a movable armature for the actuation of the valve and with magnetic means for moving the armature towards the magnetic device. A non-magnetic material is provided on a portion of the armature so as to maintain a non-magnetic gap between the magnetic device and the armature. The housing, which encloses these members with a valve action, comprises a plurality of parts and is assembled from sheet-type flanged parts, packing cords and sealing rings being inserted between individual parts. A space or air gap is provided between the end face of the excitation coil and the armature, the length of this gap corresponding approximately to half the length of the winding itself; moreover, no ferromagnetic body is provided here to ensure controlled short-circuiting of the induced field.In view of the mode of construction evident ere, only relatively modest sealing forces can be exerted on the armature, irrespective of the fact that the multi-part design of the housing excludes the use of this valve in a vacuum, in particular when external forces act on the tubular sections and bending stresses are applied to the valve housing.

Specification US-A-4196751: The valve shown here, the exciting winding of which does in fact have a container of ferromagnetic material for controlled guidance of the excitation field, is not suitable for use in a high vacuum because the end face of the coil is situated directly in the valve chamber. Here too the insulation of the winding gives off gases to the vacuum and the vacuum is thereby nullified.

Furthermore, it would hardly be possible for the threaded connection between one housing part and the other housing part of this known valve to be sealed n a vacuum-tight manner.

Specification DE-A-2246624: In this valve too the coil body of the exciting winding is not closed and cannot be closed off from the valve passage space. For this reason a valve of this type also cannot be used for vacuum installations.

The staiting point for te invention is a valve of the type mentioned at the beginning and the object of the invention is to develop this type of valve in such a way that it has a sealing member which is movable with as little friction as possible and the valve is as fluidtight as possible, that is, in practice the valve housing does not need to be sealed off from the outside at any location. The sealing member is intended to be so mounted that its mobility and ease of operation are not impeded by an impurities introduced by the flow of medium passing through the valve, so that a valve designed in accordance with the invention can be used as a safety valve.

The invention is characterised in that the exciting winding is disposed in a container of circular ring-shaped cross-section, which is open at one end and consists of ferromagnetic material, the tubular portion having the valve seat passing through the central aperture of the container and, at least over part of its axial length, the central aperture of the container has a thread, by means of which this container is screwed on to an external thread on the tubular portion, the housing has two metal tubular portions whose mutual facing ends bearing the outlet openings each have a radial extension, at least one of these extensions has a rim directed towards the other extension and both parts are joined together by way of a weld seam along the outer edge of the rim, and at its open end the container has an outwardly directed radial extension which has an external thread and which is slightly larger than the diameter of the housing of circular cross-section, and a cap nut engaging over the housing is screwed on to this external thread.

The solenoid valve forming the basis of the present application has been developed for gas centrifuges in association with uranium enrichment plants. The valve acts as a safety element. A centrifuge of this type is connected to three ducts, one duct for the gas mixture to be separated and the two other ducts forth gas components separated from one another.

A centrifuge of this type operates under vacuum and in cascade connection, that is several thousand of such centrifuges are provided in plants of this type operated on an industrial basis. The centrifuge rotor rotates at high speed (approximately 40,000 rpm), the rotor diameter is about 140mm and is 3,800mm high. If the rotor of one such centrifuge in the cascade comprising several thousand centrifuges "goes down" (term used for such a failure by specialists in this field), a pressure wave is created in this centrifuge which is propagated very rapidly and causes all the other centrifuges to collapse in the manner of a domino effect, unless appropriate measures are taken to prevent the propagation of this pressure wave. A valve according to the invention serves as a preventative measure and is used for protective purposes.In order to achieve this very difficult object, these valves have to comply with specifications which do not apply in the previously-tnown constructions. Tne valve housing itself has to be vacuum-tight and, the-efore, should have as few as possible structural joints and structural planes of separation; the excitation coil must be closed off from the actual valve chamber or, otherwise, to attain rapid closing speeds (less than 25 ms) the coil must be very small so as to keep its time constant low, the latter being critical for the response time of the coil. Nevertheless, even with a small coil a substantial closing force should be achieved so that a small gap is present between the coil and the armature, thereby obviating any escape of process gas in the event of a fault.

A valve of this type of construction is able to meet any of the specifications which have been indicated above, so that such a valve can be used as a safety valve in centrifuges for uranium enrichment plants. The coil is closed off from the actual passage space and can be of small size, the magnetic flux is controllable, the housing wall situated between the armature and the coil can be relatively thin and, as a result of a cap nut, it is nevertheless possible to provide an inherently stable structural element which can accommodate vibrations and bending stresses, without thereby impairing or having a detrimental effect on the electromagnetic specifications Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:: Figure 1 shows a first valve in longitudinal section; Figure 2 shows a cross-section along the line II-II in Figure 1; and Figure 3 shows a second valve in longitudinal section.

A first tubular portion 1 has at one of its ends a connecting socket 2, a connecting flange or a connecting thread, by means of which it can be connected to.a pipeline. At its inner end, which is in the form of a valve seat 3, this tubular portion 1 has a shield-like or flange-like radial extension 4 of relatively thin wall thickness. On the outside this extension 4 has a rim 5. The inner outlet opening of this tubular portion 1, which forms the valve seat 3, has a step-like shoulder 6. The outside of this tubular portion 1 incorporates an external thread 7 over part of its length. This tubular portion 1 and its aforementioned parts are made of magnetically non-conductive material, for example aluminium.

A disc-shaped armature 8 is provided here parallel to the plane of this extension 4 and its plane of principal extension lies at right angles to the plane of the drawing in Figure 1. In its centre zone this dsc-shaped armature 8 has a recess in which a sealing member 9 is inserted, the latter having a central projecting stud 10. This sealing member is made of suitable material, of the type used for such sealing members and the special properties of which depend on the nature of the media which flow through this valve.

The outer diameter of the circular disc-shaped armature 8 is smaller than the inner diameter of the cylindrical chamber 11 defined by the rim 5, so that this armature 8 is spaced apart on all sides from the inner wall of the rim 5.

The circular disc-shaped armature 8 is held in this position by a conical coil spring 12. The coils at one end of this spring 12 are inserted in force-locking or form-locking manner in the step-like shoulder 6, while coils at the other end of this conical spring 12 engage in force-locking and/or form-locking manner the central stud 10 of the sealing member 9, the tapering portion of this conical spring 12 being directed towards the sealing member 9. A plurality of apertures 13 in the armature 8 are provided around the sealing member 9. The sum of the.

cross-sectional areas of these apertures 13 in the armature 8 is at least as great as the internal cross-section of the tubular portion 1.

A second tubular portion 14 is arranged in alignment with the first tubular portion 1 and is also provided at its outer end with connecting means for connection to a pipeline. At its end nearest the armature 8, this tubular portion 14 is also provided with a radial extension- 15 whose peripheral contour corresponds to the first-mentioned extension 4. This extension 15 also has a rim 16, whereby this housing part abuts against the rim 5 of the first-mentioned part. Both parts are here fluidtightly joined together by a circumferential weld seam 17. In the vicinity of the rim 16 an annular projection 18 protrudes from the inside of this extension 15 towards the armature 8.

The armature 8 is applied with one end face against this projection 18 under the action of the spring 12; the apertures 13 are so arranged that they lie within the annular projection 18.

An exciting winding l9, the ends of which are directed outwards for connection to a power supply (not shown here), is accommodated in a container 20 of ferromagnetic material. This container 20 is of circular ring-shaped cross-section; that is cylindrical with an annular axially extending recess, in which the winding 19 is contained, and a central aperture or through bore. At the open end the outer edge of the container 20 is provided with a radial flange 21 which has an external thread 22, the diameter of this flange 21 being slightly larger than the diameter of the extensions 4 and 15. At its open end this container 20 abuts directly against the extension 4, the first-mentioned tubular portion passing axially tnrough the central bore of this container 20.For fastening purposes this container 20 is provided with an internal thread which is screwed on to the thread 7 of the tubular portion 1. The magnetic axis of the exciting winding 19 lies parallel to the axis of the tubular portion 1.

A cap nut 23 is screwed on to the thread 22 of the container 20 and engages over the part of the housing formed by the extensions 4 and 15.

The description so far has concerned the valve illustrated by way of example in Figures 1 and 2.

While the armature 8 is here in the form of a circular disc, this armature may be cross-shaped or in the form of a bar. Instead of one exciting winding 19, a plurality of cylindrical exciting windings can be arranged around the tubular portion 1 with their respective magnetic axes lying parallel to one another. Punctiform projections can also be provided on the inside of this part in place of the annular projection 18. It is also possible to provide an additional exciting winding on the tubular portion 14, in the manner of the first-mentioned winding, and to connect the two windings in such a way that current flows through them only alternately, a second exciting winding of this type enabling the force exerted by the spring 12 to be intensified. In such a case, it would also be advantageous for the wall thickness of the extension 15 to be made as thin as possible.

The action of the valve illustrated in Figures 1 and 2 is immediately evident from its structural design. While no current is flowing through the winding 19, that is, it is not excited, the spring 12 maintains the armature 8 within the valve chamber 11, the projection 18 ensuring that a clearly defined gap is present here. When the winding 19 is excited, the electromagnetic field induced by this excitation pulls the armature 8 towards the container 20 against the action of the spring 12 until the sealing member 9 is applied against the valve seat 3 so as to effect a seal; the valve is then closed. The armature, sealing member and valve seat are to be so formed, in respect of their axial dimensions and extension, that the end face of the sealing member 9 is applied fluidtightly against the valve seat 3 before the armature abuts with its end face against the extension4.When the excitation of the winding 19 is cut out and as soon as the magnet field has broken down, the spring 12 pushes the armature 8 back into its position shown in Figure 1, thereby-opening the valve once more. In practice, the valve housing no longer has any place which is to be sealed from the outside, other than the weld seam 17, which in view of current welding technology can be effected in a durable and fluidtight manner. In practice, the armature is mounted floating inside the chamber 11 and at no location can be paired to slide with other structural parts which could impair or even prevent its mobility.Instead of a conical spring 12, as described and illustrated here, it would also be possible to provide small laminated springs but this would not simplify the construction nor augment its usefulness. Tlle valve shown here in Figure 1 is an in-line valve.

A multi-way valve is shown in longitudinal section in Figure 3, the basic construction of which corresponds to the first-mentioned valve and like structural members and components are given the same reference numerals . The armature 8, which is also of circular disc-shaped form is so designed that the actual sealing member 9 has active sealing surfaces on both sides of the armature. Therefore, the armature 8 has a central stepped bore into which the sealing member 9 is securely fitted, the latter again consisting of material suitable for its purpose.

In place of the tubular portion 14 with its extension 15 at one end, (as illustrated by way of example in connection with Figure 1) a housing part 24 is provided with a central ore 25 and a bore 26 lying parallel thereto, these bores having external connecting sockets 27 and 28 respectively. The boundary portion of this housing part 24 nearest the tubular portion i and the armature 8 corresponds in its inside conformation to that of the extension 15. In Figure 3, the passage from the tubular portion 1 to the bore 26 is shown open. When the winding 19 is excited, the armature 8 is attracted and the passage from the bore 26 to tne bore 25 is opened, whereas the passage to the tubular portion 1 is closed.

As a result of tne so-called floating mounting of the armature 8 with the sealing member 9 its freedom of movement under the influence of the electromagnetic field or under the force exerted by the spring 12 is ensured under ail operating conditions and situations, so that a valve of the- type Xn question is extremely suitable as a safety valve which has to be used to effect emergency shut-downs.

To ensure that the pulling force of the magnet can be as fully effective as possible, the gap between the armature 3 and the extension 4 is of small size and the wall thickness of the extension 4 is also very small, for example smaller than lmm. Because of this relatively small wall thickness of less than lmm, the housing accommodating the armature 8 and the sealing member 9 does not possess particularly high bending and tensile strength. This housing does in fact provide sealing with respect to the exterior bt tensile and bending forces acting from the outside on the valve are dealt with by the container 20 and the cap nut 23, which are a mechanically robust structural member which has the purpose of accommodating externally acting forces of whatever type and of keeping them away from the fluidtight housing proper, so that despite its thin-walled nature the housing retains its prescribed shape and configuration even under unfavourable conditions, whereby correct operation is ensured because the structurally prescribed and predetermined dimensions are accurately maintained even under these conditions.

Claims (6)

CLAIMS:

1. A valve with a housing and at least one valve seat provided therein and a sealing member (9) which can be pressed against the valve seat (3), the sealing member (9) being carried by a magnetisable armature (8) and to displace the armature (8) there is provided at least one exciting winding (19) which can be connected to a power supply, the valve seat (3) being provided at one end of a straight tubular portion (1) wnicil at. its other end has means for connection to , a pipeline, and the sealing member (9) is disposed in the centre zone of an armature whose plane of principal extension is at right angles to the axis of the tubular portion (1) having the valve seat (3) and the magnetic axis of the exciting winding (19) lies parallel to the axis of this tubular portion (1) and the armature (8) is accommodated by the valve housing with clearance in peripheral direction, and a spring (12) is provided between the tubular portion (1) having the valve seat (3) and the armature (8), one end of the spring being connected with the tubular portion (1) and its other end with the armature (8), and the inner housing wall situated opposite the tubular portion (1) having the valve seat (.3) has one or more projections (18) near to the edge which protrude into the housing towards the armature (8) and against which the armature (8) is applied under the force exerted by the spring (12) when the exciting winding (19) is de-energised, and the valve housing is of multipart design and has a plane of separation, which lies on or parallel to the plane of principal extension of the armature (8), characterised in that the exciting winding (19) is disposed in a container (20) of circular ring-shaped cross-section, which is open at one end and consists of ferromagnetic material, the tubular portion (1) having the valve seat (3) passing through the central aperture of the container (20) and at least over part of its axial length, the central aperture of the container (20) has a thread, by means of which this container (20) is screwed onto an external thread (7) on the tubular portion (1), and the housing has two metal tubular portions (1,14) whose mutually facing ends bearing the outlet openings each have a radial extension (4,15), at least one of these extensions (4,15) has a rim (5,16) directed towards the other extension and both parts are joined together by way of a weld seam (17) along the outer edge of this rim (5,16), and at its open end the container (20) has an outwardly directed radial extension (21) which has an external thread (22) and which is slightly larger than the diameter of the housing of circular cross-section, and a cap nut (23) engaging over the housing is screwed on to this external thread (22).

2. A valve according to Claim 1, characterised in that the wall thickness of each extension (4), against which the container (20) accommodating the exciting winding (19) abuts from the outside with its open end, is less than that of the other extension (15).

3. A valve according to Claim 1 or 2,characterised in that the tubular portions and housing parts are made of non-magnetisable material.

4. A valve according to Claim 1, 2 or 3, characterised in that the coil spring (12) is of conical shape and the tapering end of this conical coil spring (12) is directed towards and is connected with the sealing member (9).

5. A valve which comprises a first member (1) having a duct, a second member (4,24) having a duct, the first and second members being welded together (17) to form a chamber (11) into which the ducts open, an armature (8) and a spring (12) disposed inside the chamber, the spring biasing the armature to close the duct of the second member (14), a container (20) which comprises a cylindrical body having an annular axially extending recess and a central through bore, a winding (19) disposed in the recess, the first member (1) having a tubular portion which extends through the central through bore, the central through bore and the tubular portion having co-operating screw-threads (7), the first member having a radially -extending wall facing the open end of the annular recess of the container, a screw-threaded cap (23) extending around the first and second members and engaging the second member and the container.

6. A valve substantially as herein described with reference to and as shown in the accompanying drawings.